The present invention relates to an improved noise damper for compressed air devices.
From DE 102 48 183 A1 it is known that insulating materials can be used in the form of a knitted fabric roll in noise dampers of compressed air devices. Such a knitted fabric roll is made from a tubular knitted fabric produced on a circular knitting machine from warp knit thermoplastic fibres having, for example, rectangular cross section, by cutting a knitted fabric tube to a predetermined length and heat sealing it at its cut faces in such a way that a rectangular tubular portion is obtained. This rectangular tubular portion is then rolled up to obtain a knitted fabric roll. The knitted fabric roll is then pushed into a connecting tube leading to the atmosphere. Aside from the fact that it is necessary to use an additional connecting tube, which requires a large amount of installation space, and that it is necessary to take additional measures to ensure that the knitted fabric roll is held sufficiently in place in the connecting tube, the resulting noise damping is not satisfactory.
DE 42 37 630 A1 describes a compressed air venting device that has a primary air path routed from an inlet of a housing via noise damping means to an outlet, and a secondary air path provided parallel thereto and comprising a first sub-channel extending from the inlet and a second sub-channel formed by the outlet or leading to the outlet. The two sub-channels are not filled with the noise damping means. The two sub-channels are in communication with one another via the noise damping means. The two sub-channels and that part of the noise damping means which places the two sub-channels in communication are arranged in such a way that such part of the noise damping means opens up a direct communication path between the two sub-channels when a dynamic pressure is admitted. The noise damping means are formed by a filtering knitted fabric, which comprises a stocking-like woven part of plastic flat wire, which is wound in the form of a roll. The housing is composed of one housing part resembling a pot and another housing part formed as a cover to be snapped thereon. A disadvantage of this compressed air venting device used as a noise damper is that the danger of leaks causing a loud noise level exists at the joints of the housing parts. Moreover, the known device is relatively bulky, and therefore requires considerable installation space.